In bonding the bond pads on the semiconductor chip to lead frame fingers in an automatic bonder, it is necessary to first align the semiconductor chip and then bond the lead frame individual lead fingers to the bond pads on the semiconductor chip using a wire bonder.
Prior bonding systems used "Dead Reckoning" or estimation using two points on the lead frame to orientate the lead frame and identify the location of the rest of the lead frame fingers. This system works as long as the lead frame fingers are properly located. Bent or tilted fingers, due to lead frame floatation in glass, and manufacturing variations, displace the lead frame fingers from its normal position. Since bonding to the lead frame finger takes place at the position where the lead frame finger should be if the finger is displaced. This can result in improper connection or no connection at all. This results in a manufacturing blemish and loss of yield.
Systems have been developed that visually display the device and lead frame by video camera at the bonding station. These systems usually use a video cursor two point alignment on the lead frame and chip pad, for example, two corners of the chip. The lead frame fingers are then located using two point data. From the known orientation of the chip and the orientation of the lead frame, the bond pads on the chip are stitch bonded to the lead frame finger. Bent or misaligned lead frame fingers can result in improper bonding of the semiconductor chip to the lead frame fingers.